Internal combustion engine exhaust filter with pressure relief

ABSTRACT

An exhaust filtration system including a gap upstream of the filter and a regular pressure device downstream of the filter to thus normally maintain a pressure differential across the filter but operative to, upon build up of pressure upstream of the filter provide for relief to the atmosphere.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to filtration systems for internal combustion engines.

2. Description of the Prior Art

With any internal combustion engine, it is desirable to treat the exhaust before emission to the atmosphere. In many engines, one of the operating problems is the presence of gaseous pollutants (CO, NO_(x), CO₂, etc.) and fine solid particles in the exhaust. Many different types of filtration systems have been proposed for filtering the impurities from the exhaust.

Problems have been encountered when filters, such as carbon filters become saturated or clogged, thus diminishing their effectiveness and in some instances building up back pressure which may be deleterious to the continued operation of the engine.

Efforts have been made in the past to address issues involving warm up or overheating of an internal combustion engine exhaust filters. One such effort led to the proposal of a control valve downstream of the filter and responsive to cold temperatures to close and divert the exhaust from a bypass path through the filter. When the engine heats up the valve is opened to allow the exhaust to bypass the filter. A device of this type is shown in U.S. Pat. No. 5,223,009 to Schuster. While effective to direct control through the filter during warm up, such devices suffer the shortcoming that, in the event of the filter becoming clogged, flow directed through the filter itself may create a back pressure which, over a period of time could damage the engine.

Other efforts to control exhaust flow through a filter have focused on diesel engines where the exhaust may, under certain conditions, reach upwards of 1,100° F. These efforts have led to proposal of a system including a filter bed of steel wool or the like where carbon particles are collected during warm up and wherein flow from the engine is divided to divert a minor part while some is re-circulated from downstream of the filter to balance the fuel and oxygen content in effort to maintain the desired temperature in the filter bed.

A system of this type is shown in U.S. Pat. No. 4,217,757 to Crone. While having utility to control the temperature in the filter bed, such systems suffer the shortcoming that pressure build up from the filter clogging or the like can lead to a high back pressure against the engine.

Other efforts have focused on burning of the soot produced by diesel engines. These efforts have led to a proposal that a particulate filter be connected with a diesel engine to collect soot which may be oxidized by introducing forced air to the filter. A valve controls exhaust flow to a filter bypass in response to the engine speed. A system of this type is shown in Japanese Patent No. JP404183917 to Shimoda. While having advantages for controlling the flow of exhaust from a diesel engine, systems of this type are extremely complicated, expensive to make, complicated to control and pose the problem that, should flow through the filter be hindered when the bypass valve is closed backpressure can build up at the engine exhaust manifold.

SUMMARY OF THE INVENTION

The exhaust filtration system of the present invention is characterized by an opening between the engine exhaust pipe and filter inlet pipe sized to, under normal operating conditions, induce flow to the filter, but responsive to a pressure build up in the filter, vent exhaust directly to the atmosphere.

Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a filter incorporated in the internal combustion engine exhaust system of the present invention;

FIG. 2 is a longitudinal (broken) sectional view, in enlarged scale, taken along the lines 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view taken along the lines 3-3 of FIG. 2;

FIG. 4 is a transverse sectional view taken along the lines 4-4 of FIG. 2;

FIG. 5 is a side view, in reduced scale, of an internal combustion engine exhaust filter system incorporating the filter shown in FIG. 1;

FIG. 6 is a transverse sectional view taken along the lines 6-6 of FIG. 5;

FIG. 7 is a longitudinal sectional view taken along the lines 7-7 of FIG. 5;

FIG. 8 is a sectional view similar to FIG. 7 but showing relief of the exhaust flow;

FIG. 9 is a longitudinal sectional view similar to FIG. 7 and depicting a first modification of the system of the present invention;

FIG. 10 is a transverse sectional view taken along the lines 10-10 of FIG. 9;

FIG. 11 is a longitudinal sectional view similar to FIG. 7 and depicting a second modification of the system and present invention;

FIG. 12 is a longitudinal sectional view similar to FIG. 7 and depicting a third modification of the system and present invention;

FIG. 13 is a longitudinal sectional view similar to FIG. 7 and depicting a fourth modification of the system and present invention;

FIG. 14 is a longitudinal sectional view similar to FIG. 7 but depicting a fifth modification of the present invention; and

FIG. 15 is a longitudinal sectional view similar to FIG. 7 but depicting a sixth modification of the system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 2 and 5, the high pressure release exhaust filter apparatus of the present invention includes, generally, a filter 25 having its inlet 27 connected with an inlet pipe 29 which is in fluid communication with a exhaust pipe 31 across a gap 33. The outlet from the filter 25 includes a powered suction fan or other low pressure device such as a blower, generally designated 37, for creating a pressure drop across a filter bed 39 or the like.

An internal combustion engine typically incorporates an exhaust pipe 31 leading to a filter for filtering hydrocarbon residue from the exhaust prior to emission to the atmosphere. It is of concern that, when the filter becomes plugged raising resistance to flow, damage can be done to the engine from build up of back pressure.

The present invention incorporates a space defining the gap 33 between the terminal end of the exhaust pipe 31 and inlet end to the inlet pipe 29 leading to the filter 25 to, upon elevation of pressure at the inlet to the filter exhaust to atmosphere ahead of the filter.

Outlet from the filter 25 is typically exhausted through a tail pipe or the like to atmosphere. In the preferred embodiment, my invention includes the blower 37 driven by an electric motor 40, and which may be connected in electric circuit with the engine system and in some embodiments includes a speed control responsive to different engine conditions, such as RPM's, for adjusting the speed of the blower 37 to increase the blower speed at heavier loads and greater exhaust flow.

As will be appreciated by those skilled in the art, an exhaust pipe may have a diameter of about 2½ inches and the gap 33 should be at least 1/16^(th) of an inch or more long to afford sufficient cross sectional for escape of the exhaust flow where in the event the filter becomes clogged and may, in fact, take many different forms. In one embodiment, the gap may be from about 1 to 2 inches in length, it being appreciated that the gap need only be sufficiently great to allow for substantially full transfer of flow from the exhaust pipe 31 to the inlet pipe 29 during normal operation. In the event of a back up from the filter resulting in pressure in the inlet pipe 29 being increased above a certain range the gap will allow for escape of exhaust from the gap. The length of the gap will be selected to match the operating characteristics of the engine but must be sufficiently short so the negative pressure in the inlet pipe 29 under normal operating conditions will draw substantially all the exhaust into such pipe to flow through the filter. Those of skill in the art will select the size and shape for the particular engine exhaust characteristics. A negative pressure device, such as the blower 37, will draw exhaust flow from the filter at 39 to generate a negative pressure to increase the pressure differential across the gap 33 during normal operation to thereby capture substantially the entire flow from the exhaust pipe 31 to the inlet pipe 29.

Referring to FIG. 7, in the preferred embodiment of the filtration system of the present invention includes the inlet pipe 29 of a diameter somewhat greater than the diameter of the exhaust pipe 31 so as to, favorably induce flow from such exhaust pipe into the inlet pipe 29 as indicated by the directional arrows 53.

As noted, in this configuration, should the pressure build up in the inlet pipe 29 above a normal range the gap forming the relief device will allow for escape of exhaust from the exhaust pipe 31 as depicted by the directional arrow 55 in FIG. 8.

As it will be appreciated by those skilled in the art, during normal operation, the lower 37 will be actuated to draw a negative pressure on the downstream side of the filter bed 39 to facilitate a relatively high rate of flow through the inlet pipe 29 and through the filter bed 39. Under normal engine operating conditions, the blower 37 provides sufficient flow rate to afford a negative pressure in the inlet pipe 29, preferably of about 1 psi, to combine with the several psi positive pressure in the exhaust pipe 31 to afford a pressure differential across the gap 33 of several psi such that the rather forceful ejection of exhaust from the pipe 31, combined with the negative pressure drawing that exhaust into the inlet pipe 29, provides for substantially full transfer of exhaust flow from the exhaust pipe 31 to the inlet pipe 29. This then provides for substantially complete flow of the exhaust into the filter 25 and across the filter bed 39 through the blower 37 and out the tail pipe 34. Preferably the flow is balanced to the point where a quantity of atmospheric air, typically about 10% of the full flow stream, is drawn into the inlet pipe to facilitate cooling of the filter. It is also noted that the air gap 33 acts as a thermal barrier to limit transfer of heat from the high temperature exhaust pipe to limit heating of the filter.

As the engine conditions vary, the speed controller in the motor 41 will adjust the speed of the blower 37 to correspondingly adjust the flow rate through the pipe 29 and filter 25 to control magnitude of negative pressure drawn within the inlet pipe 29. For instance, as the engine is revved up, the speed 41 will proportionally increase the speed of the blower 37 to increase the negative pressure drawn on the downstream side of the filter bed 39, the consequent pressure differential across the filter bed 39 and thus the magnitude of negative pressure in the inlet pipe 29 will further increase the pressure differential across the gap 33 to further enhance the tendency of the system to draw the exhaust expelled from the exhaust pipe into the inlet pipe 29.

As will be appreciated by those skilled in the art, the blower 37 may take the form of any desirable negative pressure device for drawing a negative pressure in the inlet pipe to induce exhaust flow from the exhaust pipe, across the pressure relief exemplified by the gap 33 and through the filter, it only being important that the pressure be reduced, as by a venture or partial vacuum device.

As will be further appreciated by those skilled in the art, should the filter bed 39 become clogged or flow there through be otherwise obstructed, the exhaust being expelled into the inlet pipe 29 will tend to build pressure up therein and as such pressure increases above a normal operating range, the pressure differential across the gap 33 will be decreased and even reversed to the point where the pressure is greater in the inlet pipe thereby tending to spill the exhaust from the exhaust pipe 31 out through the gap 33 to escape to atmosphere thereby avoiding excessive pressure on the filter bed 39 to thereby avoid unwanted high pressure in the exhaust pipe 31, which could result in unwanted back pressure against the exhaust from the internal combustion engine. Malfunctioning of the filter will quickly be detected and, when time permits, repairs may be made to return the system to its normal operating condition. In the meantime, the system will be protected against over pressurizing in a relatively foolproof manner.

It will be appreciated by those skilled in the art that the construction of the pressure release device shown in FIG. 7 may take many different forms such as a wall constructed of a perforated screen or metal fluted or otherwise ventilated connection. The gap may be formed by positioning the end of the exhaust pipe 31 flush with the end of the inlet pipe 51 or, in some instances, even telescoping the outlet extremity of the exhaust pipe 31 a limited degree into the inlet pipe 57.

In some instances, the exhaust pipe 31 will be telescoped sufficiently far into the inlet pipe 51 to provide approximately a 4″ inch linear overlap.

Referring to FIGS. 9 and 10, in some modifications of the filtration system, the end of the exhaust pipe 31 and inlet to the inlet pipe 29 defining the gap may be connected together by longitudinal ribs 59 spaced equidistance circumferentially thereabout to provide for structural interconnection between the two pipes to secure the desired longitudinal spacing while leaving ample escape capacity.

Referring to FIG. 11, the pipes 29 and 31 may be connected together by longitudinal ribs 65 which are based equidistance thereabout and are of a generally C-shaped longitudinal cross sectional shape.

Referring to FIG. 12, it will be appreciated that the exhaust pipe may be formed with a bell shaped outlet 67 which may terminate in an outlet opening having a diameter substantially larger than the diameter of the inlet pipe 29 to cooperate therewith in defining an annular gap 68 forming to pressure release.

Referring to FIG. 13, as will be appreciated by those skilled in the art, in this modification the exhaust pipe 31 is formed with a linear bell coupling 71, also of a substantially larger diameter than the diameter of the inlet pipe 29 to define an annular shield spanning the front side of the gap 33 and gap 72.

Referring to FIG. 14, the pipes 29 and 31 extend transversely of the direction of travel for the vehicle powered by the engine and the relief device includes an arcuate shield spanning the front side of the gap 33 and 75 connected with radial posts 77 to the pipes 29 and 31 to shield against incoming air stemming from forward accelerators of the vehicle.

Referring to FIG. 15, here the gap 33 from the exhaust pipe 31 to the inlet pipe 29 is bridged by a transversely projecting large diameter open ended stub cross pipe 81 which provides for, upon the pressure in the inlet pipe being raised above the normal range, escape in diametrically opposite directions out the ends of the cross pipe 81.

From the foregoing, it will be appreciated that the engine exhaust filtration system of the present invention provides an economical and reliable means for avoiding excessive back pressure on the engine system.

As will be appreciated by those skilled in the art, the pressure release configuration of the present invention is relatively independent of original equipment exhaust systems and thus does not detract from the operation thereof. It can be readily retrofitted into original equipment exhaust system. In many embodiments, the pressure release device provides for an air gap between the exhaust and tail pipes which acts as a thermal barrier limiting the rate of heat transfer from the exhaust pipe to the intake pipe. In some embodiments, the pressure release device provides for the introduction of a small quantity of ambient air to be mixed with the exhaust gases and actually facilitates cooling of the exhaust gases passing through the filter. 

1. An internal combustion exhaust filtration system for filtering exhaust from an internal combustion engine and comprising: a filter for filtering the exhaust; an exhaust pipe from the engine for flowing the exhaust and terminating in a downstream end; an inlet pipe having an upstream end and a downstream end connected to the filter; a pressure release device responsive to the pressure differential between the inlet pipe exceeding a predetermined differential to relieve exhaust flow from the exhaust pipe; and a pressure reducer for reducing pressure downstream of the pressure relief device.
 2. The exhaust filtration system of claim 1 wherein: the downstream end of the exhaust pipe and the upstream end of the inlet pipe are spaced apart to define the pressure release device.
 3. The exhaust filtration system of claim 1 wherein: the pressure reducer is in the form of a blower downstream of the release device for drawing the exhaust from the device toward the filter.
 4. The exhaust filtration system of claim 1 wherein: the exhaust pipe and inlet pipes are axially aligned.
 5. The exhaust filtration system of claim 1 wherein; one of the pipes is of a larger cross section than the other.
 6. The exhaust filtration system of claim 1 wherein: the pipes are of the same diameter.
 7. The exhaust filtration system of claim 1 wherein: the pressure release device includes at least one connector between the exhaust and inlet pipes.
 8. The exhaust filtration system of claim 1 wherein: the pressure reducer is disposed downstream in the filter.
 9. The exhaust filtration system of claim 1 wherein: the pressure reducer includes a blower downstream for drawing exhaust from the filter.
 10. The filtration exhaust system of claim 2 wherein: the downstream end of the exhaust pipe and upstream end of the inlet pipe are spaced apart a distance of between 1 and two inches.
 11. The filtration exhaust system of claim 2 wherein: the inlet pipe is formed with a larger cross section than the exhaust pipe and the ends of the pipes are spaced apart a distance of at least 1/16^(th) of an inch.
 12. The filtration exhaust system of claim 2 wherein: the ends of the pipe are spaced apart at least 1 inch.
 13. The filtration system of claim 2 that includes: a pipe device configured with an opening find the release system
 16. 14. An internal combustion filtration system for exhausting exhaust from the engine at a normal range of flow and comprising: an exhaust system including a filter and a release device upstream of the filter, operative in response to the flow through the filter dropping below the lower end of the range to release flow of exhaust from the exhaust system.
 15. An internal combustion filtration system for exhausting exhaust from an engine and comprising: a filter for filtering the exhaust; a pipe device leading from the engine to the filter and including at least two pipes having ends spaced apart a distance sufficient to, during normal operating conditions effect transfer of a substantial portion of the exhaust flow from the engine to the filter and operative end response to the pressure in the filter building up beyond a predetermined pressure to release exhaust to the atmosphere; and a pressure reduction device disposed downstream of the pressure release device for reducing the pressure downstream of the pressure release device.
 16. The filtration system of claim 15 wherein: the pipe device includes at least two pipes.
 17. A filtration system of claim 15 wherein: the pressure release device is configured to release exhaust directly to the atmosphere.
 18. The filtration system of claim 15 wherein: the pipe device is constructed to, under normal operation, provide for unobstructed flow to the filter. 